Good game but needs some tweaking, it's a bit too tough and frantic as it stands.
I felt everything moved way too fast so I didn't feel in control. Ship left/right was too quick. Maybe make the sprites a bit smaller to make some room to dodge & so top to bottom movement of enemies give you more time to react.
Need some feedback the enemies get hit rather than just disappear. Also some feed back that you are getting hit would help - not just the health bar.
Some variety in the enemies or what they shoot would be good too - maybe that comes in later levels but I wasn't able to survive long enough to see those.
Some progression to make the game a bit easier to start with would be good too.
I think a littlle more development could turn this into a great little space shooter.